Compound Interest Calculator
See how your money grows over time.
Enter your numbers and press Calculate.
About the Compound Interest Calculator
Compound interest is interest earned on both the original principal and the interest already added. This calculator projects a balance forward using a starting amount, a regular contribution, an annual rate, and a compounding frequency.
The output separates total contributions from total interest so you can see how much of the growth came from compounding. Time and rate both matter, but longer time horizons are where compounding has the largest effect.
How this works
FV = P(1 + r/n)^(nt) + C·[((1 + r/n)^(nt) − 1) / (r/n)]
Assumptions
- Interest compounds at the selected frequency.
- Contributions are made at the end of each period.
- The interest rate is fixed for the entire period.
Frequently asked questions
What does compounding frequency change?
More frequent compounding (monthly versus annual) slightly increases the effective yield, because interest starts earning interest sooner.
Is this the same as an investment return?
The math is the same, but investment returns are not fixed. Use a steady rate here only as a simplified projection.
Why does the interest portion grow faster later?
Because it is a percentage of a larger balance each period, the amount added compounds and accelerates over time.
Related tools
This calculator provides estimates for educational purposes only and is not personalized financial advice. Rates, taxes, and financial products change — verify with providers and qualified professionals.